THE MAST CELLS 



together (Fig. 60) an excellent correlation between mast cells and histamine 

 is seen to exist throughout the entire thickness of the skin. 



Discussion 



It is clear from the data which have been presented that in every species 

 examined the quantity and distribution of the histamine in skin is paralleled 

 by the relative density and distribution of the tissue mast cells. Taken in 

 conjunction with previous work on mast cells and histamine in normal tissues, 

 and especially in view of the very high histamine contents of mast-cell tumours 

 from dogs, it would seem highly probable that histamine in general is concen- 

 trated in the mast cells. This conclusion is supported by a recent account by 

 Graham and associates (1955) on the relationship of histamine to mast cells 

 in the skin of the normal dog. 



In the present work we see, first, that the curiously high mast-cell content 

 in the skin of the ear has its counterpart in a high histamine content of similar 

 regional distribution. Secondly, when samples of abdominal skin from various 

 species are split into an inner and an outer layer, both the histamine and the 

 mast cells become subdivided and partitioned in the same way. This is well 

 seen in those three species in which the skin histamine is high — cat, mouse, and 

 rat. The cat and rat differ in that the histamine and mast cells lie mainly in 

 the outer and inner layers of the skin respectively. The mouse shows a com- 

 bination of both patterns in having a double layer of mast cells, outer and 

 inner, and a correspondingly high histamine value in each. Thirdly, when the 

 skin of the cat is split into multiple layers and their mast cells are counted, a 

 'histamine profile' can be constructed which corresponds closely with the mast- 

 cell values at the various levels. 



In comparison with the findings in cat, mouse, and rat, the mast-cell and 

 histamine contents of human skin are not unduly high, though high values have 

 been recorded earlier in this work for certain pathological tissues rich in mast 

 cells, as in urticaria pigmentosa. Thus it would appear that the cytological 

 location of tissue histamine is the mast cell, and that the gross values for 

 histamine which have for long been recorded are, in the main, a reflection of the 

 extent to which the tissue or organ contains mast cells. The present results 

 indicate that this concept of the location of histamine in mast cells is applicable 

 to the skin, the organ on which much of the classical work on histamine is based. 



THE MAST-CELL REACTION IN PRECANCEROUS SKIN 



OF MICE 



As stated in the introduction to this book, my interest in the mast cell was 

 first aroused many years ago by a chance remark of one of my teachers who 



152 



